German Patent No. 1,296,133 and the corresponding British Patent No. 1,164,407 as well as German Patent No. 1,544,080 and the corresponding U.S. Pat. No. 3,453,835 disclose the desulfurization of gases in processes in which physically acting solvents, such as methanol, xylene, N-methylpyrrolidone (NMP) and acetone are used.
The physically active solvents differ from chemically acting scrubbing solutions in that their dissolving or solubilizing power depends to a first approximation on the partial pressure of the substances to be absorbed and on the temperature at which the gas is scrubbed. The solubility of a gaseous substance increases as the temperature decreases and as the partial pressure increases. For this reason the solvent which is laden with sulfur compounds can be regenerated in known manner by a temperature rise and/or by a temperature relief.
In the known processes, difficulties arise because the solvents have no selective activity as regards the sulfur compounds but dissolve also other compounds, particularly C0.sub.2, which are contained in the gases. The C0.sub.2 content of the solvent will oppose a selective desulfurization so that more solvent will be required in the known processes.